The aim of this study is to trace and establish the correlations between the vegetative (average number, average height, and average thickness of shoots) and reproductive characteristics (average fruit weight and average yield) of the Bulgarski Rubin cultivar grown in the semi-mountainous conditions of the Central Balkan Mountains. Bulgarian raspberry varieties are adapted to our soil and climatic conditions and successfully realize their genetic potential in them. The study was conducted during the period 2018-2020 in a demonstration plantation of Research Institute of Mountain Stockbreeding and Agriculture, Troyan, which was established in 2016, with a planting scheme of 3.00/0.50 m. The study was carried out in two stages: the first stage was carried out in 2018, and the second stage was carried out in 2019. Statistical analyses show a high correlation between the average number of shoots and the average yield during the first two experimental years, and very high in the third year. During the three-year period, a very high correlation was found between the vegetative indicators of average height and average shoot thickness.

The highbush blueberry is a fruit crop with specific requirements for agroclimatic conditions. Limiting factors for its distribution are its increased demands for atmospheric humidity and soil acidity. It thrives successfully in mountainous and semi-mountainous regions of the country, where there is a higher amount of precipitation, increased air humidity, and relatively favorable temperatures for realizing its biological potential. The growth and development of five american varieties of highbush blueberries: Bluecrop, Bluegold, Patriot, Spartan, and Toro, were monitored in a demonstrative plantation at the RIMSA in Troyan, during the period 2020-2022. Under the agroclimatic conditions of the Pre-Balkans, fruit ripening of the studied highbush blueberry varieties begins from the second ten-day period of June, with no significant differences in timing between them. The quantity of plant pigments (chlorophyll a, chlorophyll b, and f -carotene) in leaf samples from the studied varieties was analyzed during the three-year experimental period. The highest levels of chlorophyll a and f -carotene in leaf samples were found in the second year of the experiment in The tallest average bush height was recorded in the Spartan varieties - 113.39 cm and Bluecrop - 110.11 cm during the experimental period. The best results in terms of average yield were recorded in Toro (103.85 g/bush) and Bluecrop (99.94 g/bush). The fruit weight had the highest average values in the Toro varieties - 1.69 g and Bluecrop - 1.45 g, while the fruits of the Spartan - 1.02 g and Patriot - 1.12 g varieties had the lowest weight.

The aim of the study was to investigate the quality parameters of some berries under natural grassing conditions, in the inter-rows. The experiment was conducted in the period 2023-2024 in a demonstration plantation of the Research Institute of Mountain Stockbreeding and Agriculture, Troyan (Bulgaria) on light grey forest soils. Three blueberry cultivars (Bluecrop, Patriot and Toro) and three blackcurrant cultivars (Byurlovskaya, Ometta and Ben Lomond) were the objects of the study. The data on the biochemical indicators of the study indicate that blueberry and blackcurrant fruits have a high (valuable) biological value. The analysis of blueberry fruit revealed a lack of sucrose in the first experimental year and a very limited sucrose content in the second (0.01 % - Bluecrop and 0.06 % - Patriot). The highest anthocyanin content was found in the cultivar Patriot (85.56-161.50 mg/%) for the genus Vaccinium and in the cultivar Ben Lomond (290.37 mg %) for the genus Ribes. The relative share of cereal varieties in the interrows of Vaccinium corymbosum L. correlated positively with the contents of total sugars (r = 0.666), inverted sugar (r = 0.669) and acids (as malic) (r = 0.975), and the amount of legumes with the contents of sucrose (r = 0.640) and ascorbic acid (r = 0.987). In Ribes nigrum L., the percentage of cereal meadow grasses in inter-row strips was strongly negatively correlated with the amount of sucrose (r = -1.000) and ascorbic acid (r = -0.998). Legume species showed a positive correlation with dry weight matter (r = 0.710), refractory solids (r = 0.998), total sugars (r = 0.691), invert sugar (r = 0.999), acids (as malic) (r = 0.972), tannins (r = 0.991) and pectin (r = 0.782). The natural grassland in the inter-row strips of blackcurrant has a higher content of structural fibre components and crude protein, which influences the quality of the forage as an energy source for ruminants. The qualitative analysis of the grassland in the interrows in both orchards allows its use as forage in ruminant feeding.

The article presents the results of optimizing micropropagation and ex vitro adaptation conditions for blackberry plantlets of the Rubus L. cultivars Natchez and Heaven Can Wait. During the micropropagation stage, the most effective shoot multiplication was achieved on MS medium supplemented with 0.5 mg/L BAP and 0.1 mg/L GA3, resulting in the formation of 5.3-5.8 shoots per explant with an average height of 5.27-5.43 cm. For ex vitro rooting and adaptation, the best results were obtained using a peat and perlite substrate (3:1) moistened with a 0.01% solution of succinic acid. After 8 weeks, the Natchez cultivar showed a shoot length of 8.47 cm, and Heaven Can Wait reached 7.10 cm. Both cultivars developed more than 11.42 roots on average, with root lengths ranging from 10.35 to 11.52 cm. The use of growth stimulants (humic acid, nanosilicon, and succinic acid) significantly improved rooting efficiency, with the succinic acid treatment achieving the highest results-rooting and adaptation rates of 87% to 97%. These findings confirm the effectiveness of growth stimulators in enhancing the propagation and adaptation of blackberry plantlets under ex vitro conditions.

The vegetative and reproductive traits of the blackberry cultivar Hull Thornless, grown in different agro-ecological conditions of Bulgaria, was monitored. The study was conducted during the period 2022-2024 in a collection plantation of Agriculture of Trakia University - Stara Zagora. The indicators of average number, average height (m) and thickness of shoots (mm) of two linear meters of the inter-row area were monitored. The results show that the studied parameters were influenced by environmental factors during the study. Regarding vegetative indicators, the number of shoots (17 +/- 6.34), the thickness of the shoots (14.85 mm +/- 2.36) and the height of the shoots (3.49 m +/- 0.32) are greater in the blackberry grown in the conditions of Troyan. During the tested period, the highest average yield (1666.33 g/2m) and average fruit weight (5.63 g) was recorded by the plants in the plantation of Stara Zagora.

The scientific experiment was conducted in a demonstration plantation at the Research Institute of Mountain Stockbreeding and Agriculture of Troyan. A fertilizing scheme was applied to aronia shrubs with various types of fertilizers, as well as combinations among them. The biochemical composition of aronia berries was compared after harvest and after one year of storage at -18 degrees C. High values of dry weight, dry matter by Re, pectin, and total polyphenols were identified in the potassium sulfate fertilizing variant. The combined fertilizing with triple superphosphate, potassium sulfate, and carbamide gave the highest content of total sugars, sucrose and total polyphenols in fruits after the storage period. Statistical differences were proven among fertilizing variants in terms of dry matter by Re, total sugars, sucrose, and ascorbic acid. Organic acids, anthocyanins, and total polyphenols had proven results. The objective of the present study is to analyze the changes in the biochemical composition of aronia berries after the application of various fertilizing variants, after harvest, and one-year storage period.

In recent decades, the attention of scientists has been focused on the fruits of Vaccinium L. due to their significant potential to be used in the food, pharmaceutical, and cosmetic industries. In the present experiment, the biochemical composition of fruits of four introduced highbush blueberry varieties (Bluecrop, Bluegold, Spartan, Toro) grown in a demonstration plantation of RIMSA-Troyan was analyzed. The changes in the biochemical composition of fresh and frozen fruits after 1-year of storage at - 18 degrees C (in refrigerated conditions) were compared. The fresh fruits of Bluegold are distinguished by a higher content of total and inverted sugar, ascorbic acid, tannins, anthocyanins, and pectin than the other studied varieties. In Bluecrop fruits, after one year of storage under refrigerated conditions, higher content of dry matter weight, ascorbic acid, tannins, and pectin were reported. The best results in terms of colour brightness were reported for fruits of the Spartan variety (22.68).

The aim of the present study is to develop a system for micropropagation of bog blueberries. They are distributed from 1700 to 2500 m above sea level in the mountains Rila, Pirin, Western and Central Balkan Mountain, Vitosha, Osogovo, Western Sredna Gora and Western and Middle Rhodopes. An approach for the statistical optimization of micropropagation media under laboratory conditions has been applied for the first time. Sterile explants were introduced in vitro on WPM, enriched with 3 mg.l-1 2-iP and pH 4.2. To optimize proliferation, nine variants of WPM were tested with the addition of growth regulators (zeatin and 2-iP) in varying concentrations (1.5 - 3.5 mg.l-1), organic additives (casein hydrolisate and myo-inositol and pH values (4.3 - 4.8). The best result regarding the reproduction coefficient was found on M1 nutrient medium (3.77 pcs/explant), enriched with 3.5 mg.l-1 zeatin and 2-iP, 250 mg.l-1 casein hydrolisate, pH 4.8. The largest average length of shoots was reported on the modified medium M9 with 2.63 cm. The resulting micro shoots were rooted on WPM nutrient medium, halved macrosol content and different levels of IAA (0.5 - 1 mg.l-1), myo-inositol and pH. The highest percentage of rooting was found on R8 nutrient medium with 56.7%.

The scientific experiment was conducted in the period 2018-2020 in a collection plantation of the Research Institute of Mountain Stockbreeding and Agriculture in Bulgaria. The plantation was created in the autumn of 2016. The planting scheme of the plants is 3.00/0.50 m. The objective of the study is 'Tulameen' cultivar. Vegetative parameters were monitored: average number of shoots, average thickness and average height of shoots and reproductive: average fruit weight and yield per linear meter. The number of shoots had the highest values in the first year of the experiment (29.33), and their height (1.51 m) and thickness (7.60 mm) in the second year. The highest yield was recorded in the third year (1.48 kg/1 m2). A high to very high positive correlation between shoot height and thickness was reported in all three years. In the first year, a high correlation dependence was registered between shoot height and yield (0.76) and negative in the second (-0.85) and third (-0.51) years of the experiment.

The present study follows the dynamics of nutrient elements in the soil of a raspberry plantation during the period of blossoming and fruit harvesting. The scientific experiment was conducted in the period 2018-2020 in a collection plantation of the Research Institute of Mountain Stockbreeding and Agriculture in Troyan with four raspberry genotypes, such as Willamette, Meeker, Samodiva and Magdalena. The soils of the region are gray forest, moderately eroded, low in humus and prone to waterlogging.The content of basic nutrients (nitrogen, phosphorus, potassium), humus and pH in the 0-20 cm and 20-40 cm soil layers was analyzed. The results show that the highest nitrogen content was registered the surface soil layer with 89.77 mg/kg during the blossoming phenophase in 2019.The amount of phosphorus varied widely 2.60-6.20 mg/100 g. The highest potassium content (28.66 mg/100g) was found again in the surface soil layer during blossoming of the 2020 raspberry plants.

The scientific experiment was conducted during the period of 2018-2020 in a collection plantation of the Research Institute of Mountain Stockbreeding and Agriculture in Troyan. The object of the study is the 'Shopska Alena' raspberry cultivar. The plantation was created in the autumn of 2016. Correlation analyzes were made between the vegetative indicators: number, height and thickness of the shoots with the yield. The highest values for height (1.38 m) and thickness (8.41 mm) of the shoots were recorded in the second year of the experiment, and the highest yield was obtained in the third year -1.69 kg/1m2. A high correlation dependence between the height and thickness of the shoots was recorded through all three years and between the height and thickness with the yield in the second and third year.

The interconnections between the vegetative and reproductive manifestations of the candidate raspberry cultivar 'Magda-lena' were monitored. The scientific experiment was conducted in a collection plantation of the Research Institute of Mountain Stockbreeding and Agriculture in Troyan in the period of (2018-2020). The field experiment is based at intra-row spacings between plants (0.50 m and 0.30 m) and inter-row spacings of 3.00 m. The indicators, such as average number of shoots, aver-age height and average thickness of shoots, average fruit weight (g), and average yield (g) per one linear meter of the intra-row area. The largest number of shoots (35.50) for the candidate cultivar 'Magdalena' was found in the planting spacing of 0.30 m variant, while the highest height of shoots (183.15) was registered at the larger (0.50 m) planting distance. The average thick-ness of the shoots varied from 6.31 mm to 7.52 mm. Significantly higher yields were found for 'Magdalena' candidate cultivar at the shorter planting distance in the first two experimental years, and this regularity changed in 2020, when the highest aver-age yield from the tested period was reported (2543.67 g/m), but at 0.50 m planting distance. The highest average fruit weight of 3.30 g was reported from the greater planting distance in 2018.

The present study observed the content of biologically active compounds in raspberry leaves in different phenophases (full blossoming, fruit harvesting and after fruit harvesting) and two stages of agrotechnics (0.50 m, 0.30 m). The study was conducted during the period 2019-2020 in a collection plantation of the Research Institute of Mountain Stockbreeding and Agriculture in Troyan with two introduced raspberry cultivars `Willamette' and `Meeker`. The field experiment is based at intra-row spacings between plants (0.50 m and 0.30 m) and inter-row spacings of 3.00 m. The content of biologically active compounds in the leaves was found during the phenophases: full blossoming, fruit harvesting and after fruit harvesting. The results show that the highest content of the studied indicators chlorophyll "a", chlorophyll "b" and ss-carotene in the leaf samples is the cultivar Willamette, with a variant of 0.50 m, respectively (2.56 mg/g FW, 1.62 mg/g FW, 1.44 mg/g FW), from 2019 in the phenophase of full blossoming of plants. In the Meeker cultivar, the highest content of chlorophyll "a" and ss-carotene was found from the variant of 0.50 m in 2019 in the phenophase of full blossoming (1.80 mg/g FW, 1.10 mg/g FW) and chlorophyll "b" from the same variant after fruit harvest for 2020-1.04 mg/g FW.

The objective of the experiment was to trace the correlation dependences between the vegetative and reproductive manifes-tations of 'Meeker' raspberry cultivar. The field experiment was set at a row spacing of 3.00 m and two variants of intra-row spacing - 0.50 m and 0.30 m. The scientific experiment was conducted in a collection plantation of the Research Institute of Mountain Stockbreeding and Agriculture in Troyan in the period of (2018-2020). The vegetative indicators and reproductive indicators, such as number of shoots, height and thickness of shoots per one linear meter of intra-row area were analyzed and also fruit weight (g), and yield per 1 linear m. In the first experimental year, the largest average number of shoots (23.00) was found from the shorter planting distance and the largest average plant height (216.59 cm) of the same variant. The average thickness of the shoots in "Meeker " cultivar was in the range from 5.98 mm (0.50 m) to 7.59 mm (0.50). The highest average yield of 1838.50 g/m was reported from the second variant of planting in 2020, while the highest average fruit weight of 3.07g was registered in the same variant, but in 2018.

The impact of the applied fertilizers and the drying process on the quality characteristics of the plums was determined. It was found that the applied agrotechnics had an impact on certain characteristics of fresh fruits from the studied variants. The measured colour coordinates of fresh plums showed that the method of cultivation (P < 0.05) had an impact on the brightness of the variants. The colour saturation had significantly been affected by the fruits with applied chicken manure, while the fruits of the other variants had values close to the control. It was found that the drying, using a heat pump dryer with temperature of t = 43 +/- 2 degrees C and f = 10%, did not significantly affect the quantitative values of fruit colour, brightness, red colour tone, colour tone and saturation (P > 0.05).

The production of Vaccinium sp. has been a growing worldwide interest after understending their importance for diet and human health. The aim of the work was direct regeneration, propagation and rooting of axillary buds isolated from five highbush blue-berry cultivars 'Bluecrop', 'Bluegold' 'Bluejay', 'Spartan' and 'Patriot' and adapt of suitable protocol, developed and applied for Vaccinium corymbosum L. cultivars in our laboratory. For micropropagation, a basal cultural medium WPM was used, supplemented with 3.0 mg/L zeatin and 2.0 mg/1 2-iP, pH 4.2. The highest proliferation capacity was reported for cv. 'Bluegold' after fourth passage of sub cultivation (4.4 shoots per explant) and the largest length of the shoots was reported for the cv. 'Bluejay' (3.9 cm). The rooting ability was established on the same basal medium (WPM) with half-reduced salt concentration enriched with 1.0 mg/L IAA, pH 4.2. The high rooting percentage (33.3%) and the highest average number of roots (3.9) was reported for cv. 'Spartan' and 'Patriot'. The results demonstrate that regeneration potential is genotyp dependent.

The aim was to observe some characteristics dependences between vegetative and reproductive characteristics of a candidate raspberry cultivar `Troyanski biser' at the foothill environment with over wetting soils. The scientific experiment was conducted during the period of 2018-2020 in a collection plantation of the Research Institute of Mountain Stockbreeding and Agriculture in Troyan. The objective of study was a candidate cultivar `Troyanski biser' propagated through in vitro technology. The vegetative and reproductive indicators were analyzed, such as average number of shoots (1 m(2)), average height (cm) and average thickness (mm) of shoots and average fruit weight (g), and average yield (kg/1 m(2)). The largest average number of shoots were formed in 2018 (17.33 total number) during the experimental period. The highest average height (146 cm) was registered during the same year. The highest values for the average thickness were registered in 2019 (9.14 mm). The average yield was comparatively stable for the whole period, as it was the highest for the second experimental year (1.33 kg).

The scientific experiment was conducted during the period of 2018-2019 in a collection plantation of the Research Institute of Mountain Stockbreeding and Agriculture in Troyan with two introduced raspberry cultivars, 'Willamette' and 'Meeker'. The field experiment is based at intra-row spacings between plants (0.50 m and 0.30 m) and inter-row spacings of 3.00 m. The content of mineral elements in the leaves was found during the phenophases, such as full blossoming and fruit harvesting. The results show that 'Willamette' had the highest nitrogen content in the leaf samples in the variant of 0.50 m (3.37%) in 2019 during the phenophase of full blossoming of plants. The phosphorus amount had the highest value in the variant of 0.50 m in 'Meeker' cultivar, as it was 0.27% in the phenophase of full blossoming and 0.28% in fruit harvesting phenophase in the first experimental year. Of the studied elements, the highest content of potassium was reported during the fruit harvesting phenophase in 2018 for 'Willamette' and 'Meeker' at shorter planting distances (0.70%).